Linear motor, and linear compressor using the same

ABSTRACT

A linear motor of the present invention has: a stator having a stationary iron core and a magnet wire; a mover having a moving iron core and a magnet; and a plate-shaped elastic member for supporting the mover in a manner to rock in the rocking directions. This construction eliminates a sliding portion for supporting the mover so that it can reduce the loss, which might otherwise accompany the reciprocation of the mover. Moreover, a linear compressor using this linear motor is high in efficiency and reliability.

TECHNICAL FIELD

[0001] The present invention relates to a linear motor and a linearcompressor using the linear motor and used in a refrigerating cycle orthe like.

BACKGROUND ART

[0002] In recent years, a necessity for a high efficiency of arefrigerating apparatus rises more and more. For this necessity, acompressor using a linear motor is expected to reduce the sliding lossdrastically because it has a simple mechanical construction. Therefore,the compressor is widely employed to raise the efficiency of therefrigerating apparatus. A conventional linear compressor will bedescribed with reference to the accompanying drawing.

[0003]FIG. 21 is a sectional view of the conventional linear compressor.A closed casing (as will be called the “case”) 1 houses a body 3 havinga linear motor 2 and reserves lubricating oil 4.

[0004] The linear motor 2 is constructed of a stator 9 and a mover 12.The stator 9 is composed of a first silicon steel sheet layer (as willbe called the “steel sheet layer”) 6 having a hollow cylinder shape, anda second silicon steel sheet layer (as will be called the “steel sheetlayer”) 8 of a hollow cylinder shape provided with a coil 7 and formedat a predetermined clearance on the outer circumference of the steelsheet layer 6. Both the steel sheet layers 6 and 8 are held in a frame5. The mover 12 is loosely inserted between the steel sheet layer 6 andthe steel sheet layer 8 and is formed into a hollow cylinder shape byadhering a plurality of magnets 11 to the distal end portion of a magnetshell 10 made of a non-magneticmaterial. Here, themagnets 11 aregenerallymade of a magnet material of a rare earth element having aferromagnetic field such as neodymium, and are magnetized in a directionperpendicular to the rocking direction of the mover 12.

[0005] A cylinder 14 having a cylindrical bore and a piston 15 insertedreciprocally in the cylinder 14 construct a bearing section 16inbetween. The piston 15 and the magnet shell 10 are integrally formedin a coaxial shape. Moreover, the cylinder 14 is arranged on the innerside of the steel sheet layer 6 formed in a hollow cylinder shape, andhas the frame 5 formed on its outer circumference.

[0006] The piston 15 is formed into such a hollow cylinder shape as toform a suction passage (as will be called the “passage”) 17 in itsinternal space. In the open end of the passage 17 on the side of acompression chamber 18, there is mounted a suction valve (as will becalled the “valve”) 19. A discharge valve (as will be called the“valve”) 20 is also arranged in the open end of the compression chamber18.

[0007] The cylinder 14, the piston 15 and the steel layers 6 and 8 sharetheir axes. The piston 16 retains the mover 12 through the bearingsection 16 between itself and the cylinder 14. As a result, the magnet11 holds predetermined clearances between itself and the steel sheetlayer 6 and the steel sheet layer 8, respectively.

[0008] Both an inner resonance spring (as will be called the “spring”)21 and an outer resonance spring (as will be called the “spring”) 22 arecompression coil springs. The spring 21 is arranged to contact with thesteel sheet layer 6 and the magnet shell 10, and the spring 22 isarranged to contact with the magnet shell 10 and an outer frame 23. Boththe springs 21 and 22 are assembled in compressed states. On the otherhand, an oil pump 24 is formed in the bottom portion of the body 3 andis positioned in the lubricating oil 4.

[0009] Here will be described the actions of the linear compressor thusconstructed.

[0010] First of all, when an electric current is fed to magnetize thecoil 7, a loop of a series of magnetic fluxes is generated to form amagnetic circuit from the steel sheet layer 6 to the clearance, themagnet 11, the clearance, the steel sheet layer 8, the clearance, themagnet 11, the clearance and the steel sheet layer 6. The magnet 11 isattracted by the magnet poles, which are formed in the steel sheet layer8 by those magnetic fluxes. When the electric current to the coil 7 thenalternates, the mover 12 reciprocates horizontally in FIG. 21 betweenthe steel sheet layer 6 and the steel sheet layer 8. As a result, thepiston 15 connected to the mover 12 reciprocates in the cylinder 14. Bythe reciprocating motion, the coolant gas in the space of the case 1 issucked via the passage 17 out of the valve 19 into the compressionchamber 18 so that it is compressed in the compression chamber 18 anddischarged from the valve 20.

[0011] The spring 21 is sandwiched between the cylinder 14 and the steelsheet layer 6 and supports the inner side of the mover 12 elastically.The spring 22 supports the outer side of the mover 12 elastically. Whenthe mover 12 reciprocates, the springs 21 and 22 convert the linearreciprocation of the piston 15 and store them as an elastic energy. Thespring 21 and the spring 22 induce the resonating motions whileconverting the stored elastic energy into linear motions.

[0012] On the other hand, the oil pump 24 is caused to feed thelubricating oil to the bearing section 16 by the vibrations of thecompressor body 3. Such a compressor is disclosed in Japanese PatentUnexamined Publication No. 2001-73942, for example.

[0013] In the conventional construction described above, however, themover 12 rocks between the steel sheet layer 6 and the steel sheet layer8. Specifically, it is necessary that the mover 12 be prevented fromcontacting with both the steel sheet layers 6 and 8. For this necessity,the clearances are individually formed between the mover 12 and thesteel sheet layers 6 and 8. However, these clearances of the two layersact as the magnetic resistances to reduce the magnetic fluxes inproportion to the distances. In order to achieve a thrust needed fordriving the mover 12, however, it is necessary to increase the electriccurrent to be fed to the coil 7 in an excess to compensate the reductionin the magnetic fluxes due to the two clearances. As a result, theelectric current to be inputted increases to make it difficult toenhance the efficiency.

[0014] In order to achieve the thrust needed for driving the mover 12,on the other hand, the magnet 11 has to be enlarged in the conventionallinear motor. However, the magnet 11 employs an expensive rare earthelement as its material so that the cost drastically rises to the higherlevel as the magnet 11 becomes larger.

[0015] If there is a difference in the distances between the clearancesto be formed between the mover 12 and the steel sheet layers 6 and 8,moreover, an unbalance in the magnetic attractions occurs between themagnet 11 and the steel sheet layers 6 and 8. As a result, a wrenchingforce perpendicular to the rocking directions of the mover 12 isgenerated so that a sliding loss occurs at the bearing section 16composed of the piston 15 and the cylinder 14. Alternatively, anabnormal wear occurs at the bearing section 16 to shorten the lifetimeof the compressor. On the other hand, noises are caused by the slide incase the wrenching force between the piston 15 and the cylinder 14 is sohigh as to cause the wear. Therefore, it is desired that the clearanceshave an equal distance at any place.

[0016] For avoiding this trouble, there is a method for enlarging thedistances of the two clearances thereby to reduce the ratio of thedifferences in the distances. In this construction, however, it isnecessary not only to increase the input for the necessary thrust butalso to enlarge the magnet 11. It is, therefore, customary to enhancethe working precision of the drive system containing the magnet shell10. In order to enhance the working precision, the magnet shell 10acting as the moving part has to be thickened for a higher rigidity. Asa result, the drive system has an increased weight. And the thrustnecessary for driving the mover 12 increases to make it necessary toincrease the electric current to be fed to the coil 7. Moreover, theload to be borne by the bearing section 16 rises to increase the slidingloss.

[0017] On the other hand, the magnet shell 10 and the piston 15 areconnected to each other outside of the steel sheet layers 6 and 8, andthe spring 21 is arranged between the magnet shell 10 and the steelsheet layer 6. Therefore, the magnet shell 10 has an axially long shape.In this shape, the rigidity is liable to become low especially at thedistal end portion carrying the magnet 11. For retaining the precision,therefore, it is necessary to enhance the rigidity. For this necessity,countermeasures are taken by making the sheet thicker thereby toincrease the weight more.

[0018] Moreover, it is essential for reducing the unbalance of themagnetic attractions that the assembly be made highly precise for evenclearances, in addition to the working precision. Because of the twoclearances, both the clearances inside and outside of the magnet shell10 have to be managed to make the management of the precision strict atmanufacturing thereby to raise the cost.

[0019] If the magnet shell 10 of the hollow cylinder shape is formed ofa thin sheet for the lower weight, the rigidity of the magnet shell 10or its supporting structure is insufficient. As a consequence, theunbalance of the magnetic attractions occurs due to the variation in theparts precision, the assembly precision or the magnetic force of themagnet 11, and the supporting structure is deformed so that the magnet11 is radially attracted. Then, the magnet 11 and the steel sheet layers6 and 8 approach respectively in the two clearances of the two layersthereby to cause the vicious circle, in which the magnetic attractionsare intensified more to make the eccentricity of the magnet 11 more. Asa result, the magnet shell 10 is subjected to a serious force so that itis deformed to generate noises. In the worst case, the steel sheetlayers 6 and 8 and the magnet 11 collide against each other to cause abreakage.

DISCLOSURE OF THE INVENTION

[0020] A linear motor of the present invention has: a stator including astationary iron core and a magnet wire; a mover including a moving ironcore and a magnet; and plate-shaped elastic members for supporting themover in a manner to rock in the rocking directions. Moreover, a linearcompressor of the present invention has: the aforementioned linearmotor; a cylinder sharing an axis in the rocking directions of themover; and a piston inserted reciprocally in the cylinder and connectedto the mover.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a sectional side elevation of a linear motor accordingto a first exemplary embodiment of the present invention.

[0022]FIG. 2 is a schematic diagram showing relative positions of planarsprings in the linear motor of FIG. 1.

[0023]FIG. 3 is an exploded perspective view of the linear motor of FIG.1.

[0024]FIG. 4 is a schematic diagram showing the action principle of thelinear motor of FIG. 1.

[0025]FIG. 5 is a schematic diagram showing the flow of an electriccurrent in the linear motor of FIG. 1.

[0026]FIG. 6 is a sectional side elevation of a linear compressoraccording to a second exemplary embodiment of the present invention.

[0027]FIG. 7 is a horizontal section of FIG. 6.

[0028]FIG. 8 is a sectional side elevation of a linear compressoraccording to a third exemplary embodiment of the present invention.

[0029]FIG. 9 is a sectional side elevation of a linear compressoraccording to a fourth exemplary embodiment of the present invention.

[0030]FIG. 10 is a sectional side elevation of a linear compressoraccording to a fifth exemplary embodiment of the present invention.

[0031]FIG. 11 is a sectional side elevation of a linear compressoraccording to a sixth exemplary embodiment of the present invention.

[0032]FIG. 12 is a sectional side elevation of a linear motor accordingto a seventh exemplary embodiment of the present invention.

[0033]FIG. 13 is a sectional view taken along line A-A of FIG. 12.

[0034]FIG. 14 is a plan view of a flexure bearing to be used in thelinear motor according to a seventh exemplary embodiment of the presentinvention.

[0035]FIG. 15 is a sectional view of a linear motor according to aeighth exemplary embodiment of the present invention.

[0036]FIG. 16 is a sectional view of a linear motor according to a ninthexemplary embodiment of the present invention.

[0037]FIG. 17 is a sectional view of a linear compressor according to atenth exemplary embodiment of the present invention.

[0038]FIG. 18 is a sectional view of an essential portion of a linearcompressor according to an eleventh exemplary embodiment of the presentinvention.

[0039]FIG. 19 is a sectional view of an essential portion of a linearcompressor according to a twelfth exemplary embodiment of the presentinvention.

[0040]FIG. 20 is a sectional view of a linear compressor according to athirtieth exemplary embodiment 13 of the present invention.

[0041]FIG. 21 is a sectional view of a conventional linear compressor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0042] Embodiments of a linear motor and a linear compressor accordingto the invention will be described with reference to the accompanyingdrawings. Here in the individual embodiments, the detailed descriptionon components having similar constructions will be omitted bydesignating them by the common reference numerals.

[0043] (Exemplary Embodiment 1)

[0044]FIG. 1 is a sectional side elevation of a linear motor accordingto the first exemplary embodiment of the present invention. FIG. 2 is aschematic diagram showing the relative positions of planar springs, andperspectively takes a.mover 31, a stator 35 and a planar spring 42B fromthe side of a planar spring 42A in FIG. 3. FIG. 3 is an explodedperspective view showing the assembly of the linear motor, FIG. 4 is aschematic diagram showing the action principle of the linear motor, andFIG. 5 is a schematic diagram showing the directions, in which theelectric current of the linear motor flows.

[0045] The stator 25 of a generally cylindrical shape includes twomagnet wires 26A and 26B wound in a ring shape, a stationary iron core27, and a frame 28 supporting the outer circumference of the stationaryiron core 27. The stationary iron core 27 houses the magnet wires 26Aand 26B and forms three magnet poles 29A, 29B and 29C on its innercircumference.

[0046] The stationary iron core 27 is formed by arraying silicon steelsheets (not shown), which are magnetically non-oriented and highlypermeable and which are represented by a non-oriented electromagneticsteel strip of JIS C2552, for example, radially with respect to the axisof the cylinder. The stationary iron core 27 is assembled by forming themagnet poles 29A, 29B and 29C on the inner circumference and by clampingthe magnet wires 26A and 26B wound in advance in the ring shape.

[0047] The end portions 26C, 26D, 26E and 26F of the coils of the magnetwires 26A and 26B are led out of the clearances of the radially arrangedsteel sheets of the stationary iron core 27. As shown in FIG. 5, the endportions 26C, 26D, 26E and 26F are so connected that the directions forthe electric currents to flow around the axis are reversed from eachother in the magnet wires 26A and 26B. The end portions 26G and 26H areled out of the stationary iron core 27 by making use of the electricallyinsulated conductors (not shown).

[0048] The mover 31 is formed into such a generally cylindrical shape asto share the axis with the stator 25, and is housed in the stator 25 ina manner to rock in the axial directions. The mover 31 has a moving ironcore 34 and magnets 35A and 35B. The moving iron core 34 is formed byintegrating a shaft 32 made of a ferrous material, radially on the axiswith thin sheet portions 33, in which silicon steel sheets of a highpermeability are arrayed on the outer circumference of the shaft 32.Like the silicon steel sheets making the stationary iron core 27, thesheet portions 33 are made of a silicon steel sheet, which isrepresented by the non-oriented electromagnetic steel strip of JISC2552, for example. The magnets 35A and 35B are fixed by an adhesive onthe outer circumference of the moving iron core 34 through apredetermined clearance from the inner circumference of the stator 25,and is axially separated into two. The magnets 35A and 35B havedifferent magnet poles individually on the principal faces confrontingthe stationary iron core 27. The magnets 35A and 35B are made of magnetscontaining a rare earth element to have a ferromagnetic field.

[0049] End plates 36 are donut-shaped plates attached to the two endfaces of the stationary iron core 27 of the stator 25. These end plates36 improve the strength of the silicon steel sheets arrayed radially toform the stationary iron core 27. When the end plates 36 are made of anon-magnetic material such as stainless steel, moreover, the leakage ofthe magnetic fluxes from the silicon steel sheets of the stator 25 isprevented to improve the motor efficiency. For simplicity, the endplates 36 are not explicitly shown in FIG. 3.

[0050] The planar springs 42A and 42B are arranged on the both side ofaxial direction of the mover 31. The planar springs 42A and 42B have anelasticity and are made of a metal sheet with high flexibility,specifically, a ferrous material such as spring steel, tool steel orstainless steel, for example. The planar springs 42A and 42B areprovided with three through holes at three portions: a center portion42C; and distal ends 42D and 42E of the two helical arms. The centerportion 42C is jointed to the shaft 32 of the mover 31 by means of abolt, and the distal ends 42D and 42D are individually jointed to theframe 28 of the stator 25 by means of bolts. The planar springs 42A and42B construct an elastic member.

[0051] The planar spring 42A is so attached that arm portions 42F and42G leading from the center portion 42C to the distal ends 42D and 42Eare turned counter-clockwise, as viewed from the side of the planarspring 42A of FIG. 3. The planar spring 42B is also attached in asimilar manner. As shown in FIG. 3, moreover, the attaching angle of theplanar spring 42A to the frame 28 is turned by about 90 degrees from theattaching angle of the planar spring 42B to the frame 28. As a result,the positions of the arm portions 42F and 42G are not aligned on the twosides of a linear motor 43.

[0052] By these planar springs 42A and 42B, the mover 31 is supported inthe manner to rock in the axial direction while confronting the magnetpoles 29A and 29B of the stator 25 through a predetermined clearance.Thus, the mover 31, the stator 25 and so on construct the linear motor43.

[0053] The actions of the linear motor 43 thus constructed will bedescribed mainly with reference to FIG. 4.

[0054] When the magnet wires 26A and 26B are fed with the electriccurrent, magnetic fluxes Φ are generated to loop to the stationary ironcore 27, the clearance, the magnet 35A, the moving iron core 34, themagnet 35A, the clearance and the stationary iron core 27, as indicatedby arrows. Other magnetic fluxes Φ are generated to loop to thestationary iron core 27, the clearance, the magnet 35B, the moving ironcore 34, the magnet 35B, the clearance and the stationary iron core 27.By these magnetic fluxes Φ, the magnet poles 29A, 29B and 29C aremagnetized to the N-pole, the S-pole and the N-pole, respectively. Sincethe outer surfaces of the magnets 35A and 35B are magnetized to theS-pole and the N-pole, respectively, the forces of attraction andrepulsion are generated, as indicated by blank arrows, between theindividual magnet poles and the individual magnets. As a consequence,the mover 31 is driven in the direction of arrow X.

[0055] Next, when the magnet wires 26A and 26B are fed with the electriccurrent in the reverse direction, the actions reversed from theaforementioned ones occur to drive the mover 31 in the direction opposedto that of the arrow X. The mover 31 is reciprocally moved by makingcontrols to switch the direction and magnitude of the electric currentalternately.

[0056] The magnets 35A and 35B are fixed on the outer circumference ofthe moving iron core 34. As compared with the conventional linear motorwith moving magnet, therefore, the clearances in the magnetic flux loopare reduced because of the absence of the clearance between the magnets35A and 35B and the moving iron core 34. As a result, the magneticresistance is lowered to allow the magnetic fluxes to flow more easilythan in the conventional linear motor. Therefore, the electric currentto be fed to the magnet wires 26A and 26B for generating a predeterminedmagnetic flux for a necessary thrust can be reduced to improve theefficiency or to reduce the amount of magnetism.

[0057] Since the magnets 35A and 35B are adhered to the moving iron core34, the mover 31 can have a strong structure and can easily improve theprecision of the external diameter size. Moreover, the intensity of themagnets, as might otherwise be fragile, is compensated by themselves. Asa result, the magnets made of the expensive rare earth element can bethinned to lower the cost drastically, and the moving portion islightened to improve the efficiency.

[0058] Moreover, the mover 31 is supported by the planar springs 42A and42B with respect to the stator 25, and these planar springs 42A and 42Bhave a higher radial rigidity than the spring constant in the axialdirection. Therefore, even if an unbalance or the like in the load ofthe weight of the mover 31 or in the magnetic attraction acts betweenthe mover 31 and the stator 25, the change in the clearance between themover 31 and the stator 25 is remarkably small. It is, therefore,possible to prevent the mover 31 from being deformed to cause the noisesand from colliding against the stator 25.

[0059] The planar springs 42A and 42B have the relatively longer armportions, as compared with the radius, because the arm portions 42F and42G extend while turning in the same direction. Therefore, the rockingamplitude within the elastic range is so large as to relax the increasein the stresses of the springs.

[0060] Moreover, both the planar springs 42A and 42B are so attached asto turn counter-clockwise, as viewed from the side of the planar spring42A of FIG. 3. Moreover, the arm portions 42F and 42G have the identicalturning direction. As a consequence, the turning directions, which arecaused by the fine torsion of the two springs accompanying thereciprocation are also identical. Therefore, it is possible to preventthe increase in the stress, which might otherwise be caused when thetorsion is restricted by the slight turn of the mover 31 of thecylindrical shape, thereby to improve the reliability.

[0061] When the mover 31 is to be fixed relative to the stator 25through the planar springs 42A and 42B, an even clearance has to beretained by inserting a plurality of clearance gauges of thin sheetshapes having small width between the mover 31 and the stator 25. Whenthe planar springs 42A and 42B are arranged on the two end faces of thelinear motor 43, however, the clearance between the mover 31 and thestator 25 is hidden behind the planar springs 42A and 42B. As aconsequence, the exposed clearance is reduced, as shown in FIG. 2. Inthis embodiment, however, the planar springs 42A and 42B are arranged atthe attaching angles of 90 degrees on the two sides of the mover 31. Asa consequence, the clearance gauges can be inserted all over thecircumference by inserting them from the two sides of the motor.Therefore, the even clearance can be retained by connecting the mover 31and the stator 25 through the planar springs 42A and 42B after theclearance gauges were inserted. As a result, the wrenching force, whichmight otherwise be generated due to the unbalance of the magneticattractions, can be prevented to reduce the generation of the slidingloss and to prevent the wear.

[0062] The stationary iron core 27 is divided into three blocks in theaxial direction across the section containing the housing portions ofthe magnet wires 26A and 26B. Therefore, the assembly can be made byinserting the magnet wires 26A and 26B wound in advance in the ringshape, in a clamping manner, thereby to achieve a high productionefficiency.

[0063] In this embodiment, the stator 25 has the three magnet poles, themover 31 has the two magnets arranged in the axial direction. However,the motor can also be constructed even if the stator has two magnetpoles or four or more magnet poles. In short, it is sufficient that thestator is provided with a plurality of magnet poles and that the moveris provided with magnets of a number less by one than magnet pole numberof the stator.

[0064] The flows of the magnetic fluxes in the stationary iron core 27turns their directions by about 90 degrees between the magnet poles 29A,29B and 29C and the outer circumference side of the magnet wires 26A and26B. However, the stationary iron core 27 is made of the non-orientedelectromagnetic steel strip. So, the permeability has no orientation nomatter what direction the magnetic fluxes might flow in. Therefore, noserious efficiency drop occurs.

[0065] (Exemplary Embodiment 2)

[0066]FIG. 6 is a sectional side elevation of a linear compressoraccording to the second exemplary embodiment of the present invention,and FIG. 7 is a horizontal section of FIG. 6. A closed casing (as willbe called the “case”) 41 houses a compressor body 53 having the linearmotor 43.

[0067] In a cylinder 51 connected to the stator 25 of the linear motor43, there is reciprocally inserted a piston 52, which is connected tothe mover 31 of the linear motor 43. To the end face of the cylinder 51,there are attached a cylinder head 54 and a suction muffler 55. Thecylinder head 54, the suction muffler 55, the cylinder 51, the stator 25and so on form a stationary unit 57.

[0068] A moving unit 58 is composed of the piston 52, the mover 31 andso on. The piston 52 is attached to the distal end of the shaft 32 ofthe mover 31, and the shaft 32 and the piston 52 are rotatably connectedto each other through a ball joint 61. The planar springs 42A and 42Bare individually attached at their center portions to the moving unit 58and at their two distal end portions to the stationary unit 57 therebyto construct a resonance spring 59. The cylinder 51 is attached to theframe 28 of the stator 25 of the linear motor 43, and the piston 52 isinserted in a rocking manner into the inner face 51A of the tubelikecylinder 51.

[0069] The compressor body 53 is so elastically supported by suspensionsprings 64 that the linear motor 43 may reciprocate substantiallyhorizontally in the case 41. A capillary tube 66 is dipped at its oneend in lubricating oil 44 reserved in the bottom portion of the case 41,and is opened at its other end in a tube portion 55A of the suctionmuffler 55.

[0070] Here will be described the actions of the linear compressor thusconstructed. When the linear motor 43 is fed with the electric current,the mover 31 reciprocates so that the piston 52 attached theretoreciprocates in the cylinder 51 to act as the compressor. At this time,the frequency of the electric current is set in the vicinity of theresonance frequency, which is determined by the mass of the stationaryunit 57 and the moving unit 58 and the spring constant of the resonancespring 59 so that the linear motor 43 reciprocates efficiently withlittle energy loss by the resonance actions.

[0071] When the coolant gas is sucked from the suction muffler 55 into acompression chamber 48, the lubricating oil 44 is fed from the capillarytube 66 to lubricate the sliding portions between the piston 52 and thecylinder 51. The load to act between the mover 31 and the stator 25 issupported by the planar springs 42A and 42B so that the sideway forcehardly acts on the sliding portions between the piston 52 and thecylinder 51. On the other hand, the piston 52 and the mover 31 areconnected through the ball joint 61. Even with a small deviation betweenthe rocking directions of the linear motor 43 and the axis of thecylinder 51 due to the influence of precision of parts size or assembly,therefore, the ball joint 61 rotates to prevent the wrench between thepiston 52 and the cylinder 51. It is, therefore, possible to prevent thedrop in the efficiency, as might otherwise be caused by the increase inthe sliding loss, and the drop in the reliability, as might otherwise becaused by the friction.

[0072] In the linear compressor according to this embodiment, thecylinder 51, the planar spring 42B, the motor 43 and the planar spring42A are arranged in tandem in the axial direction and in the recitedorder. In short, the linear compressor is constructed to have thegenerally horizontal rocking direction of the mover 31. Therefore, thediameter can be made smaller than that of the conventional linearcompressor, in which the cylinder is arranged in the motor. By arrangingthat linear compressor to have a horizontal axis, the overall height canbe made smaller than that of the conventional compressor. As a result,the volume of the mechanical chamber for housing the compressor isreduced when the compressor is mounted in a refrigerator, so that thecapacity of the refrigerator is enlarged.

[0073] Moreover, the moving unit 58 is reliably supported by the planarsprings 42A and 42B so that its weight does not act as the contact loadof the cylinder 51 and the piston 52 even if the compressor is placed ina horizontally lying position. Therefore, it is possible to prevent thedrop in the efficiency, as might otherwise be caused by the increase inthe sliding loss, and the drop in the reliability, as might otherwise becaused by the friction.

[0074] (Exemplary Embodiment 3)

[0075]FIG. 8 is a sectional view of a linear compressor according to thethird exemplary embodiment 3 of the present invention. A piston 71 andthe mover 31 are connected to each other through a compliance rod (aswill be called the “rod”) 72. The remaining constructions are similar tothose of the second embodiment.

[0076] The rod 72 is constructed of such a radially small rod-shapedelastic member as has transverse flexibility and elasticity whileretaining a rigidity for supporting the load in the axial direction.Specifically, the rod 72 is made of a metallic material having anelasticity and a rigidity, such as stainless steel or spring steel.Namely, the rod 72 can move in parallel with the axis of the piston 71and is flexible in the rotating direction. Even with a small deviationbetween the shaft 32 of the mover 31 and the axis of the cylinder 51,therefore, the wrench between the piston 71 and the cylinder 51 isprevented to prevent the friction and the wear.

[0077] (Exemplary Embodiment 4)

[0078]FIG. 9 is a sectional view of a linear compressor according to thefourth exemplary embodiment of the present invention. A cylinder 81 isprovided with a gas passage 81B, which communicates with a high-pressurechamber 54A of the cylinder head 54 and the position of an internal face81A confronting the piston 52, thereby to form a gas bearing 82.Moreover, in this embodiment the lubricating oil 44 and the capillarytube 66 are not provided, because the lubricating oil in not necessary.The remaining constructions are similar to those of the secondembodiment, as shown in FIG. 6.

[0079] In the gas bearing 82, the piston 52 is held in a floating statewith respect to the cylinder 81 by the high-pressure coolant gas fedfrom the high-pressure chamber 54A of the cylinder head 54. Generally, agas bearing has a remarkably low friction because it prevents thecontact between the solids. In order to bear a heavy load, however, itis necessary to feed a large amount of gas, and a gas leakage causes aloss when the gas bearing is used between the piston 52 and the cylinder81 of the compressor. In this embodiment, the mover 31 is supported bythe planar springs 42A and 42B so that only a low load acts on the gasbearing 82. This makes it sufficient to feed a small amount of gas tothe gas bearing 82. Moreover, the ball joint 61 prevents theinclinations of the piston 52 and the cylinder 81. This reduces both thesliding loss and the leakage loss. As a result, the efficiency of thecompressor is improved, and the reliability is prevented from beingdegraded by the friction.

[0080] Because of no use of the lubricating oil, the heat transfer faceof the heat exchanger of a cooling system is not wetted with thelubricating oil so that the heat transfer with the coolant is improvedto improve the efficiency of the cooling system. Accordingly as thecoolant is not dissolved in the lubricating oil, the amount of thecoolant to be used in the cooling system can be reduced not only tolower the cost but also to improve the efficiency of the heat exchangein the cooling system and accordingly the efficiency of the coolingsystem as a whole. In the case of using a natural coolant or acombustible coolant, moreover, the amount of coolant to be used can bereduced to lower the inflammability and explosiveness of the coolant, ifleaked, thereby to improve the safety.

[0081] (Exemplary Embodiment 5)

[0082]FIG. 10 is a sectional view of a linear compressor according tothe fifth exemplary embodiment of the present invention. A cylinder 91is made of a self-lubricating material. Specifically, a diamond-likecarbon film is applied to the sliding face. In this embodiment, the gasbearing 82 is not provided. The remaining constructions are similar tothose of the fourth embodiment of FIG. 9.

[0083] The sliding portions of the piston 52 and the cylinder 91 bear alow load. Moreover, the surface 91A of the cylinder 91 has theself-lubricating property so that the wear is prevented without thelubricating oil thereby to retain the reliability of the slidingportions. Thus, this embodiment can achieve effects similar to those ofthe fourth embodiment.

[0084] In this embodiment, the diamond-like carbon film is used on thecylinder 91, but similar effects can be achieved even if anothermaterial such as a material having a self-lubricating property, e.g.,carbon added thereto, or a material, e.g., polytetrafluoroethylene isused.

[0085] In this embodiment, the self-lubricating material is used in thecylinder 91, but similar effects can also be achieved even if thatmaterial is used in the piston 52.

[0086] (Exemplary Embodiment 6)

[0087]FIG. 11 is a sectional view of a linear compressor according tothe sixth exemplary embodiment of the present invention. A piston 96 ismade of a ceramic material and is specifically coated on its surfacewith a film of tungsten carbide. The remaining constructions are similarto those of the fifth embodiment of FIG. 10.

[0088] The piston 96 is provided on its surface with a tungsten carbidefilm having a high wear resistance so that it is prevented from beingworn even without the lubricating oil, thereby to retain the reliabilityof the sliding portions. Moreover, effects similar to those of the fifthembodiment such as the reduction in the viscous friction is achievedbecause the lubricating oil is not used.

[0089] In this embodiment, the tungsten carbide is used as the ceramicmaterial, which may be replaced by a ceramic material such as zirconiafor the improved reliability.

[0090] Similar effects can be achieved even if the ceramic material isused not in the piston 96 but in the cylinder 51.

[0091] (Exemplary Embodiment 7)

[0092]FIG. 12 is a sectional side elevation of a linear motor accordingto the seventh exemplary embodiment of the present invention. FIG. 13 isa sectional view taken along line A-A of FIG. 12, and FIG. 14 is a planview of a flexure bearing. A mover 121 of this embodiment includes amoving iron core 124 having a core portion 121A and a sheet portion 121Bformed integrally with each other, and moving shafts 126A and 126B fixedin the core portion 121A and extended in the rocking directions. Flexurebearings 128A and 128B, which are individually arranged on the two sidesof the rocking directions of the mover 121, hold the moving shafts 126Aand 126B and support the mover 121 in a manner to rock in the rockingdirections. The remaining constructions are similar to those of thefirst embodiment. Here, this embodiment is not provided with the endfaces 36, which have been described with reference to FIG. 1, but may beprovided with the end plates 36 as in the first embodiment.

[0093] The core portion 121A is formed of a ferrous material into ahollow cylinder shape. The sheet portion 121B is formed by arrayingsilicon steel sheets on the outer periphery of the core portion 121Aradially with respect to the axis of the mover 121. The silicon steelsheets are highly permeable and which are represented by a non-orientedelectromagnetic steel strip of JIS C2552, for example. Both the movingshafts 126A and 126B are made of a nonmagnetic material such asstainless steel, which has a sufficiently higher electric resistancethan that of iron.

[0094] Each of the flexure bearings 128A and 128B is provided with eightarms 128C, 128D, 128E, 128F, 128G, 128H, 128J and 128K, which are formedby cutting eight thin slits in the plate-shaped elastic material.

[0095] The flexure bearings 128A and 128B are individually connected andfixed to the frame 28 at their outer circumference and to the movingshaft 126A or 126B at their inner circumference. The flexure bearings128A and 128B construct elastic members. These flexure bearings 128A and128B have extremely high rigidities in the radial direction butextremely lower rigidities as the elastic members in the axialdirections (or in the rocking directions) than those in the radialdirections. Therefore, the flexure bearings 128A and 128B function asbearings for supporting the mover 121 reciprocally in the axialdirections. The radial and axial rigidities vary with the design factorssuch as the shape, array, material and material thickness of the arms.The flexure bearings 128A and 128B have such radial rigidities as cansupport the force for at least the mover 121 to be attracted to thestator 25 by the magnetic attractions and can allow the mover 121 andthe stator 25 to retain a predetermined clearance all over thecircumference.

[0096] The magnets 35A and 35B and the magnet poles 29A, 29B and 29C areso arranged that the magnet 35A may confront the magnet poles 29A and29B whereas the magnet 35B may confront the magnet poles 29B and 29Ceven when the mover 121 rocks. Moreover, the mover 121 is given such alength that it does not go out of the inside of the stator 25 atrocking, and that its difference from the length of the stator 25 issubstantially equal to the maximum amplitude of the mover 121.

[0097] Here will be described the actions of the linear motor thusconstructed. When the magnet wires 26A and 26B are fed with the electriccurrent, the mover 121 is driven as in the case of the first embodimentof FIG. 4. When the direction of the electric current is reversed, themover 121 is driven in the reverse direction. The mover 121 isreciprocated by making controls to switch the direction and magnitude ofthe electric current alternately.

[0098] As in the first embodiment, the magnets 35A and 35B and themoving iron core 124 are also integrated in this embodiment. As aconsequence, the clearance contained in the magnetic flux loop isreduced to lower the magnetic resistance. Therefore, the necessarymagnetic force can be generated with little and small magnets thereby toreduce the loss in the support mechanism for supporting the wrenchingforce and the gravitational force perpendicular to the reciprocatingdirections of the mover 121.

[0099] Here, a fine turning torsion occurs in the flexure bearings 128Aand 128B according to the reciprocation of the mover 121. This turningtorsion is absorbed because the mover 121 and the stator 25 are formedinto the generally cylindrical shape sharing the axis of the mover 121in the rocking directions. As a consequence, the mover 121 holds apredetermined spatial distance from the stator 25 even if it rotates. Inother words, it is possible to prevent the problems in the reduction ofthe efficiency or the increase in the noises, which might otherwise becaused by the contact or collision between the mover 121 and the stator25.

[0100] Moreover, it is sufficient for the positional relation to alignthe axes of the mover 121 and the stator 25. In other words, theassembly for keeping the clearance constant is easier than the case, inwhich the mover 121 has a flat surface. As a result, the magneticattractions by the magnets 35A and 35B to act between the mover 121 andthe stator 25 are hardly deviated to establish little load in the radialdirections.

[0101] Moreover, the loads in the radial directions are borne by theflexure bearings 128A and 128B so that the sliding loss accompanying therocking motions of the mover 121 less occurs than that of the case ofusing the support mechanism such as slide bearings. And little loadoccurs in the sideway directions. This reduces such a rigidity in theradial directions of the flexure bearings 128A and 128B as is needed tosupport the mover 121. In other words, a low rigidity design can beperformed by reducing the number and thickness of the flexure bearings128A and 128B and the number of the arms. As a result, the hysteresisloss at the time when the flexure bearings 128A and 128B are deformed inthe rocking directions can be minimized to provide a high efficiency.Here, this hysteresis loss is described by taking a spring as anexample. The hysteresis loss is that which is caused when the energystored in the spring by compressing the spring cannot be completelyextracted as the repulsive force for the spring to extend.

[0102] Both the moving iron core 124 of the mover 121 and the stationaryiron core 27 of the stator 25 are constructed of the sheets, which arearranged radially on the axial direction. Therefore, the extendingdirection of the sheets and the magnetic flux direction are so identicalthat the magnetic permeabilities are enhanced to suppress the inductioncurrent to be generated in the iron core, thereby to reduce the loss.

[0103] Additionally in this embodiment, the moving shafts 126A and 126Bfor supporting the mover 121, the frame 28 for supporting the outercircumference of the stator 25, and the flexure bearings 128A and 128Bare made of a nonmagnetic material such as stainless steel. Therefore,it is possible to prevent the leakage of the magnetic fluxes, whichbypass the moving shafts 126A and 126B from the stationary iron core 27through the frame 28 and the flexure bearings 128A and 128B. As aresult, the induction current by the leakage magnetic fluxes can beprevented to prevent the efficiency drop of the motor. Here, similareffects can also be achieved even if a nonmagnetic material such asplastics other than the stainless steel is used for those portions.

[0104] The moving iron core 124 of the mover 121 is formed by arrangingthe sheets of the same width radially around the cylindrical coreportion 121A, so that it can be easily formed into the cylindricalshape.

[0105] Since the core portion 121A of the mover 121 is made of a ferrousmaterial, it acts as a portion of the magnetic path of the magnetic fluxloop so that the efficiency can be improved while lightening the mover121.

[0106] The vicinity of the center of the core portion 121A, which hardlycontributes strength as a structural member and the magnetic flux loopas the magnetic path, is made hollow so that the mover 121 can belightened.

[0107] Moreover, the maximum of the reciprocal distance of the mover 121is approximately equal to the difference between the lengths of themover 121 and the stator 25. As a result, it is possible to prevent themotor thrust from being lowered by the actions of the magneticattractions for the magnets 35A and 35B of the mover 121 to go out ofand into the stator 25.

[0108] The flexure bearings of this embodiment have the helical arms inthe plate-shaped elastic member but may take another shape.

[0109] The construction of this embodiment is described as the linearmotor but can also be applied, as it is, to a generator for convertingthe reciprocation into an electric current.

[0110] Moreover, the magnet wires 26A and 26B wound in the ring shapeare connected in series but may also be connected in parallel.

[0111] (Exemplary Embodiment 8)

[0112]FIG. 15 is a sectional view of a linear motor according to eighthexemplary embodiment of the present invention. Magnets 129A, 129B, 129Cand 129D having a generally arcuate sectional shape are arranged in themoving iron core 124 and are integrated with the mover 122. Theremaining constructions are identical to those of the seventhembodiment.

[0113] This embodiment achieves effects similar to those of the seventhembodiment 7. Moreover, the magnets 129A, 129B, 129C and 129D are notexposed to the surface of the mover 121, so that they have smallattractions with the magnetic material. Therefore, the handling can befacilitated by simplifying the assembly with the magnetic materialthereby to improve the mass productivity or the unit productivitydrastically. This construction may also be combined with the firstembodiment.

[0114] (Exemplary Embodiment 9)

[0115]FIG. 16 is a sectional view of a linear motor according to ninthexemplary embodiment of the present invention.

[0116] Coil springs (as will be called the “springs”) 130A and 130B arerespectively retained at their one-side ends by the moving shafts 126Aand 126B connected to the mover 121 and at their other ends by springholders (as will be called the “holders”) 131A and 131B fixed on theframe 28. The springs 130A and 130B have a smaller length (L) at theassembling time than a natural length (H) and the compression size (H-L)is large at least one half of the rocking distance of the mover 121,i.e., a stroke (S). In short, the mover 121 is pushed from its two sidesby the springs 130A and 130B.

[0117] The springs 130A and 130B decides the resonance frequency, as thetotal spring constant with the flexure bearings 128A and 128B. It isdetermined in the mass relation to the mover 121.

[0118] All the components such as the reciprocating mover 121, themoving shafts 126A and 126B, the springs 130A and 130B, the stator 25and so on are housed in the generally closed space (as will be calledthe “space”) 131C, which is constructed of the frame 28 and the holders131A and 131B.

[0119] Here will be described the actions of the linear motor thusconstructed.

[0120] When the ring-shaped magnetic wires 26A and 26B are fed with anAC current, the mover 121 is reciprocated on the same principle as thatof the seventh embodiment. When the mover 121 moves in the direction ofarrow Y, for example, the spring 130A flexes and stores a firstrepulsive force in the spring 130A. Next, when the flow direction of theelectric current changes so that when the mover 121 moves in thedirection of arrow Z, the first repulsive force is extracted from thespring 130A and is recovered as the velocity of the mover 121.Simultaneously with this, the spring 130B flexes in turn and stores asecond repulsive force in the spring 130B. When the mover 121 movesagain in the direction of arrow Y, the second repulsive force isextracted from the spring 130B and is recovered as the velocity of themover 121.

[0121] This action is the so-called “resonance action”, in which thereciprocation of a large stroke can be caused with a lower electriccurrent than that in the case of which the springs 130A and 130B are notused. The frequency of the power source at this time is equalized to theresonance frequency, which is determined from the masses of the mover121 and the stator 25 and by the spring constants of the flexurebearings 128A and 128B and the springs 130A and 130B. Then, theaccelerations from the mover 121 and the springs 130A and 130B asresonance springs are synchronized in periods. As a result, the energyloss is suppressed to a low level so that the mover 121 reciprocateshighly efficiently.

[0122] In order to raise the resonance frequency, it is necessary toreduce the weight of the mover 121 or to increase the spring constantsof the springs 130A and 130B or the flexure bearings 128A and 128B.However, the design of the motor is limited in the reduction of theweight of the mover 121. Practically, therefore, it is frequently easyto enlarge the spring constants. If the spring constants of the flexurebearings 128A and 128B are enlarged, the hysteresis loss rises to lowerthe efficiency. This is caused specifically by increasing the thicknessof the flexure bearings 128A and 128B or by overlaying the flexurebearings 128A and 128B. On the other hand, the springs 130A and 130Bbasically have no hysteresis loss. In the design for raising theresonance frequency by enlarging only the spring constants of thesprings 130A and 130B, therefore, the hysteresis loss can be reduced toretain a high efficiency.

[0123] The springs 130A and 130B have the smaller length (L) at theassembling time than the natural length (H) and the compression size(H-L) is large at least one half of the rocking distance of the mover121, i.e., the stroke (S). Even in case the mover 121 moves to themaximum in the direction of arrow Y, therefore, the length (Lb) of thespring 130B is shorter than the natural length (H). In short, the spring130B is always compressed from the natural length (H). Likewise, even incase the mover 121 moves to the maximum distance in the direction ofarrow Z, the length (La) of the spring 130A is shorter than the naturallength (H). In short, the spring 130A is always compressed from thenatural length (H).

[0124] Even if the mover 121 reciprocates, therefore, the springs 130Aand 130B are always compressed from the natural length. By the energystored by that deformation, therefore, the springs 130A and 130B areretained while being warped between the moving shafts 126A and 126B andthe holders 131A and 131B. As a result, the linear motor always repeatsthe highly efficient resonance motions. Moreover, the springs 130A and130B do not come out even without using any special fixing portion.

[0125] Moreover, all the components including the reciprocating mover121, the moving shafts 126A and 126B, the springs 130A and 130B, thestator 25 and so on are housed in the space 131C. Therefore, the noisesaccompanying the motions of the mover 121, the moving shafts 126A and126B and the springs 130A and 130B are confined in the space 131C. Inother words, the noises are less transmitted to the outside thereby toachieve the noise insulating effect.

[0126] Both the moving iron core 124 of the mover 121 and the stationaryiron core 27 of the stator 25 are constructed of the sheets, which arearranged radially on the axial direction. Therefore, noises may begenerated from the vibrating sheets when the components vibrate, but areinsulated.

[0127] In this embodiment, the springs 130A and 130B have the samespring constants, but the embodiment can be likewise made even if coilsprings of different spring constants or sizes are combined. Theresonance springs may also be constructed by combining the linear motorusing the planar springs according to the first embodiment and the coilsprings in this embodiment.

[0128] (Exemplary Embodiment 10)

[0129]FIG. 17 is a sectional view of a linear compressor according tothe tenth exemplary embodiment of the present invention. The flexurebearings 128A and 128B are clamped and fixed at their outercircumferences between the spring holders (as will be called the“holders”) 131A and 131B and the frame 28 supporting the stator 25. Onthe other hand, the inner circumferences of the flexure bearings 128Aand 128B are retained by the moving shafts 126A and 126B connected tothe mover 121 and by spring adapters (as will be called the “adapters”)132A and 132B.

[0130] The coil springs (as will be called the “springs”) 130A and 130Bare arranged on the sides of the two end faces across a linear motor 137composed of the mover 121 and the stator 25. Moreover, the springs 130Aand 130B are retained in a flexed state between the adapters 132A and132B and the holders 131A and 131B, but do not use any special fixingunit. Here, the abutting faces of the adapters 132A and 132B and theholders 131A and 131B against the interposed springs 130A and 130B areprovided with shallow steps for retaining the springs 130A and 130B.

[0131] The cylinder 51 is fixed on the holder 131B, and a cylinder cover134 is fixed on the cylinder 51. The adapter 132B is connected to thepiston 52 through the ball joint 61. The piston 52 can be freelyinclined and turned relative to the spring adapter 132B. The compressionchamber 48 is composed of the piston 52 and the cylinder 51.

[0132] Here will be described the actions of the linear compressor thusconstructed.

[0133] When the magnet wires 26A and 26B of the linear motor 137 are fedwith the AC current, the mover 121 reciprocates relative to the stator25. This driving force is transmitted through the moving shaft 126B, theadapter 132B and the ball joint 61 to the piston 52 so that the piston52 reciprocates integrally with the mover 121. By these reciprocation ofthe piston 52, the coolant gas sucked in the compression chamber 48 issequentially compressed and discharged to the outside refrigeratingcycle.

[0134] At this time, it is preferred that the frequency of the powersource to be fed to the linear motor 137 be equalized to the resonancefrequency, which is determined from the masses of the mover 121 and thestator 25 and from the spring constants of the springs 130A and 130B andthe flexure bearings 128A and 128B, as described in the ninthembodiment. As a consequence, the periods of accelerations from themover 121 and the springs 130A and 130B acting as the resonance springsare synchronized. As a result, the energy loss is suppressed to a lowvalue so that the mover 121 reciprocates highly efficiently.

[0135] The flexure bearings 128A and 128B support the mover 121 on thetwo sides so that the sliding loss accompanying the rocking motions ofthe mover 121 does not occur unlike the case using the support mechanismsuch as the slide bearings. Moreover, the rigidity needed in the radialdirections for the flexure bearings 128A and 128B is so low that the lowrigidity design can be made by reducing the number or thickness of theflexure bearings or by reducing the arm number. As a consequence, thehysteresis loss at the time when the flexure bearings 128A and 128B aredeformed can be minimized to establish a high efficiency.

[0136] Moreover, the flexure bearings 128A and 128B wholly support themagnetic attractions to act in. the radial directions of the mover 121on the two sides. As a consequence, the magnetic attractions to occurbetween the mover 121 and the stator 25 do not act as the side pressuresbetween the piston 52 and the cylinder 51 thereby to establish nosliding loss. These magnetic attractions are the forces to attract themover 121 radially relative to the stator 25. Therefore, the slidingloss is reduced to make the compressor highly efficient and to improvethe reliability of the sliding portion drastically. Even with the balljoint 61 being arranged between the adapter 132B and the piston 52,moreover, the piston 52 is supported, and the reciprocation of the mover121 are transmitted to the piston 52. When the piston 52 reciprocates inthe cylinder 51, therefore, the piston 52 is so inclined by the balljoint 61 as to rock with little axial inclination with respect to thesliding portion of the cylinder 51.

[0137] Even with the assembly, in which the mover 121 and the cylinder51 have misaligned or inclined axes, the ball joint 61 absorbs the axialmisalignment or inclination so that the piston 52 and the cylinder 51may be aligned. Without any improvement in the parts or the partsassembling precision, therefore, the side pressure between the cylinder51 and the piston 52 is reduced to reduce the sliding loss so that ahighly efficient compressor is provided.

[0138] In this embodiment, the rocking directions of the mover 121 areoriented substantially horizontal. Like the second embodiment,therefore, the diameter is made smaller than that of the conventionallinear compressor, in which the cylinder is arranged in the motor.

[0139] (Exemplary Embodiment 11)

[0140]FIG. 18 is a sectional diagram of an essential portion of a linearcompressor according to the eleventh exemplary embodiment of the presentinvention. This embodiment is so modified from the construction of thetenth embodiment that the compliance rod (as will be called the “rod”)72 described in the third embodiment is applied in place of the balljoint, and that the gas bearing 82 described in the fourth embodiment isapplied.

[0141] From the viewpoint of the strength, the rod 72 is made of amaterial such as stainless steel or aluminum to have a relatively thinportion of a circular sectional shape. This thin portion allows the rod72 to fall within the elastic deformation range in a direction inclinedfrom the axial direction.

[0142] Most of the coolant gas discharged into a high-pressure chamber134A of a cylinder cover 134 is discharged to the outside of thecompressor via a D-line 141. The remaining portion is guided via aplurality of gas passages 81B formed in a cylinder 142A to the slidingportion between a piston 139A and the cylinder 142A thereby to form thegas bearing 82. Therefore, no lubricating oil is used as in the fourthembodiment.

[0143] In the high-pressure chamber 134A, there are arranged a dischargevalve mechanism (as will be called the “valve”) 144 and a dischargespring (as will be called the “spring”) 145 for urging the valve 144onto the cylinder 142A.

[0144] A second suction tube 146 is opened at its one end 146A in thespring holder 131B in the vicinity of the opposite side of thecompression chamber of the cylinder 142A and at its other end 146B inthe closed casing 41. A suction passage 139B is formed in the piston139A, and a suction valve mechanism (as will be called the “valve”) 139Cis attached to the piston 139A on the side of the compression chamber48.

[0145] Here will be described the actions of the linear compressor thusconstructed.

[0146] The flexure bearings 128A and 128B support the magneticattractions to act in the radial directions of the mover 121, wholly onthe two sides. Therefore, the member for transmitting the reciprocationof the mover 121 to the piston 139A need not support the magneticattractions but is required of only the axial rigidity and may have alow radial rigidity. Therefore, the compliance rod 72 can be used forconnecting the piston 139A and the mover 121. As a consequence, even ifthe mover 121 and the cylinder 142A are axially misaligned or inclined,the rod 72 is so inclined or flexed that the piston 139A and thecylinder 142A may be aligned without any axial inclination. Therefore,the disadvantages in the parts precision or the parts assembly precisionare absorbed.

[0147] Without improving the parts or their assembly precision,therefore, the side pressures between the cylinder 142A and the piston139A are reduced to reduce the sliding loss. As a consequence, it ispossible to provide a highly efficient compressor and to improve thereliability of the sliding portion better.

[0148] Moreover, the rod 72 has a simpler structure than that of theball joint mechanism but does not have any sliding portion unlike theball joint mechanism, so that it has a small sliding loss and a highreliability as the connection mechanism.

[0149] On the other hand, a portion of the coolant gas discharged intothe high-pressure chamber 134A is guided via the gas passages 81B formedin the cylinder 142A, into the small clearance of the sliding portionbetween the piston 139A and the cylinder 142A. As a consequence, a gasfilm is formed to construct the gas bearing 82 thereby to bring thepiston 139A and the cylinder 142A into a non-contact state.

[0150] The gas bearing 82 is generally evaluated on how little gasquantity and how low gas pressure it can realize the non-contact statein and at. On the other hand, the performances of the gas bearing 82 arechanged according to the shape, size and location of the gas passage81B. It is, therefore, desired that a small sectional area portioncorresponding to a sectional area at the level of 30 μm to 200 μm indiameter be arranged in a portion of the gas passage 81B. If thelubricating oil exists in this construction, that small sectional areaportion is clogged with the lubricating oil to stop the coolant gas sothat the gas bearing 82 does not function. In this embodiment,therefore, not the lubricating oil but only the gas bearing 82 is used.

[0151] The piston 139A and the cylinder 142A can be held in thenon-contact state, as described above, the sliding loss between thepiston 139A and the cylinder 142A can be reduced substantially to zero.Moreover, the wear of the sliding portion is remarkably reduced toimprove the reliability drastically. The effect achieved by applyingthis construction is the higher for the compressor having the higherrunning frequency and the higher sliding loss.

[0152] Moreover, this embodiment has the oil-free construction using nolubricating oil so that it can achieve effects similar to those of thefourth embodiment.

[0153] As described above, the sliding loss is reduced substantially tozero. Since the coolant gas is introduced into the sliding portionbetween the piston 139A and the cylinder 142A, on the other hand, theleakage loss of the sliding portion increases. Since the compressedhigh-pressure gas is used in the gas bearing 82, the compression lossalso increases. However, reduction of those losses can be contained inthe design elements on the basis of the aforementioned design know-howof the gas bearing 82.

[0154] (Exemplary Embodiment 12)

[0155]FIG. 19 is a sectional view of an essential portion of a linearcompressor according to the twelfth exemplary embodiment of the presentinvention. This embodiment is constructed in the construction of theeleventh embodiment such that the material having the self-lubricatingproperty described in the fifth embodiment and the ceramic materialdescribed in the sixth embodiment are applied in place of the gasbearing to the piston and the cylinder, respectively. Specifically, apiston 139D is made of a self-lubricating material 147A, and a cylinder142B is made of a ceramic material 147B. As a consequence, by the effectof the self-lubricating property and the wear resistance of the ceramicmaterial 147B, the wear of the sliding portion is prevented to retainthe reliability even without using any lubricating oil.

[0156] The coolant gas sucked into the closed casing 41 is guided viathe second suction tube 146 into the vicinity of the opposite side ofthe compression chamber of the cylinder 142B. And, the coolant gas flowsinto the compression chamber 47 through the opposite side of thecompression chamber of the cylinder 142B, the opposite side of thecompression chamber of the piston 139D and the suction passage 139Aprovided in the piston 139D and the suction valve mechanism 139B.

[0157] The coolant gas compressed in the compression chamber 48 opensthe valve 144 against the urging force of the discharge spring 145urging the discharge valve mechanism (as will be called the “valve”) 144toward the cylinder 142B, so that it is discharged into thehigh-pressure chamber 134A.

[0158] Now at a transient running time of a cooling system such as arefrigerator, a running pressure fluctuates, and the piston 139D thenreciprocates over a predetermined stroke. In case the running electriccurrent or running voltage of the compressor is controlled, on the otherhand, the piston 139D is caused to reciprocate over a predeterminedstroke by the control precision or disturbance handling precision.

[0159] In this embodiment, the piston 139D can rock in a manner to pushout the valve 144. In the aforementioned case, therefore, the collisionimpact on the piston 139D is damped more than the discharge valvemechanism unable to perform the push-out action. Therefore, the noisesat the collision time of the piston 139D are reduced, and thereliabilities of the valve 144 and the piston 139D are improved.

[0160] (Exemplary Embodiment 13)

[0161]FIG. 20 is a sectional view of a linear compressor according tothe thirtieth exemplary embodiment of the present invention. Acompression mechanism unit 149 is so arranged upright in the closedcasing (as will be called the “case”) 41 that the rocking directions ofthe mover 121 are identical to the gravitational direction. Thecompression mechanism unit 149 is internally suspended and supported bya plurality of suspension springs (as will be called the “springs”) 150and a top spring (as will be called the “spring”) 151.

[0162] A dynamic absorber 152 is composed of a weight 153, a spring 154and a holder 155, and is formed at an upper space in the case 48. Theweight 153 is single or plural and is formed into a generally annularshape or a generally arcuate shape along the inner side of the case 41.The spring 154 is composed of springs 154A and 154B.

[0163] In the assembled state or in the stopped linear compressor state,both the springs 154A and 154B are shorter than the natural length andare compressed. As a consequence, the weight 153 is attached to theholder 155 while being clamped by the spring forces of the springs 154Aand 154B in the same directions as the rocking directions of the piston139A. The holder 155 is also formed in a generally annular shape or agenerally arcuate shape.

[0164] As the weight 153 moves, the spring 154 can be elasticallydeformed in the rocking directions of the piston 139A. Moreover, theweight of the weight 153 and the sum of the spring constants of thespring 154 in the directions for the piston 139A to rock are so selectedthat the resonance frequency determined thereby is equal to the runningfrequency of the linear compressor.

[0165] Moreover, the cylinder 142A is inserted and arranged at leastpartially in the coil spring (as will be called the “spring”) 130B.

[0166] In this embodiment, the upright arrangement is made so that therocking directions of the mover 121 are identical to the gravitationaldirection. As a consequence, force acting in the radial directions ofthe mover 121 is the magnetic attractions by the magnets 35A and 35B toact between the mover 121 and the stator 25, but not the gravitationalforce of the mover 121. Therefore, the radial rigidities of the flexurebearings 128A and 128B supporting the mover 121 and the magneticattractions can be reduced by the absence of the gravitational force ofthe mover 121. As a consequence, it is possible to select inexpensivematerials, to reduce the sheet thicknesses, to simplify the shapes or toreduce the sizes, for example.

[0167] Likewise, the side pressures due to the gravitational force ofthe piston 139A do not act on the sliding portion between the cylinder142A and the piston 139A so that the sliding loss is accordinglyreduced.

[0168] Here will be described the reduction of the vibrations by thedynamic absorber 52.

[0169] In the compression mechanism unit 149, the mover 121 reciprocatesfor compressions with respect to the stator 25. At this time, the stator25 is vibrated in the reciprocal directions of the piston 139A by thereactions of the reciprocation of the mover 121. The compressionmechanism unit 149 is elastically suspended in the case 41 by the spring150 so that its vibrations are transmitted as the exciting force throughthe spring 50 to the case 41. By the exciting force thus transmitted tothe case 41, the resonance unit composed of the weight 153 and thespring 154 is excited so that the weight 153 vibrates in thereciprocating directions of the piston 139A. At this time, the excitingforce transmitted from the spring 150 to the case 41 and the actingforce by the vibration of the weight 153 act in substantially equalmagnitudes and in opposite phases. As a consequence, the exciting forcefrom the compression mechanism unit 149 is offset by the acting forcefrom the dynamic absorber 152.

[0170] The vibration frequency of the case 41 is equal to the drivefrequency of the linear compressor. By equalizing the drive frequency ofthe linear compressor and the rocking frequency of the weight 153 of thedynamic absorber 152, therefore, the effect of the dynamic absorber 152is maximized to reduce the vibration of the case 41 to the minimum. Theresonance frequency is determined by the masses of the case 41 and theweight 153 and the spring constant of the spring 154. By selectivelydesigning the mass of the weight 153 and the spring constant of thespring 154 to be equal to the drive frequency of the linear compressor,therefore, the vibrations of the case 41 are reduced to the minimum.

[0171] Here even in case the dynamic absorber 152 is not used, theupright arrangement makes both the rocking directions of the mover 121and the extending/shrinking directions of the spring 150 identical tothe gravitational direction. As a consequence, the vibrating directionsof the case 41 also become identical to the gravitational direction. Bythe simple method of reducing the rigidity of the spring 150, therefore,the vibration transmission of the compression mechanism unit 149 to thecase 41 is reduced. In other words, the case 41 is more reduced invibrations than that of the horizontal arrangement, in which thereciprocating directions of the piston 139A are horizontal.

[0172] The dynamic absorber 152 is formed in the upper space of the case41. In the compression mechanism unit 149, the linear motor 137 is thelargest in the radial directions and determines the diametrical size,but the linear motor 137 is not arranged in the upper space of the case41. As a consequence, dead spaces are formed in the upper and in thelower with respect to the radial size of the case 41. By arranging thedynamic absorber 152 in the dead spaces, the case 41 need not beenlarged but can house compactly the dynamic absorber 152 and can reducethe vibrations.

[0173] It is especially preferred that the shape of the dynamic absorber152 be formed into the generally annular shape or the generally arcuatealong the inner side of the case 41 like the circular shape of thelinear motor 137 or the circular shape of the case 41. As a consequence,the dynamic absorber 152 is compactly housed without enlarging the case41. Moreover, the weight 153 of the dynamic absorber 152 can be enlargedor increased to widen the design range of the resonance frequency, whichis determined by the masses of the case 41 and the weight 153 and by thespring constant of the spring 154. As a consequence, the range of thedrive frequency for reducing the vibrations of the case 41 by thedynamic absorber 152 is widened to widen the running frequency range ofthe linear compressor to be driven with low vibrations.

[0174] Moreover, the cylinder 142A is inserted and arranged at leastpartially in the spring 130B. Therefore, the size of the mover 121 canbe made smaller in the rocking directions than that of the construction,in which the cylinder 142A is arranged outside of the spring 130B. As aconsequence, the case 41 can be small-sized as the linear compressorespecially in the rocking directions of the mover 121.

[0175] In this embodiment, the dynamic absorber 152 is formed in theupper space of the case 41, but similar effects can be achieved even ifthe dynamic absorber 152 is formed in the lower space of the case 41.

[0176] In this embodiment, the linear motor is arranged upward in thegravitational direction, but the linear motor can be arranged downwardin the gravitational direction.

[0177] The features of the embodiments thus far described can becombined with an allowable range, and these modifications belong to theinvention.

INDUSTRIAL APPLICABILITY

[0178] A linear motor of the present invention has: a stator having astationary iron core and a magnet wire; a mover having a moving ironcore and a magnet; and a plate-shaped elastic member for supporting themover in a manner to rock in the rocking directions. This constructioneliminates a sliding portion for supporting the mover so that it canreduce the loss, which might otherwise accompany the reciprocation ofthe mover. Moreover, a linear compressor using this linear motor is highin efficiency and reliability.

[0179] List of Reference Marks in the Drawings

[0180]1 closed casing (case)

[0181]2 linear motor

[0182]3 body

[0183]4 lubricating oil

[0184]5 frame

[0185]6 first silicon steel sheet layer

[0186]7 coil

[0187]8 second silicon steel sheet layer

[0188]9 stator

[0189]10 magnet shell

[0190]11 magnet

[0191]12 mover

[0192]14 cylinder

[0193]15 piston

[0194]16 bearing section

[0195]17 suction passage

[0196]18 compression chamber

[0197]19 suction valve

[0198]20 discharge valve

[0199]21 inner resonance spring

[0200]22 outer resonance spring

[0201]23 outer frame

[0202]24 oil pump

[0203]25 stator

[0204]26A, 26B magnet wire

[0205]27 stationary iron core

[0206]28 frame

[0207]29A, 29B, 29C magnet pole

[0208]31 mover

[0209]32 shaft

[0210]33 sheet portion

[0211]34 moving iron core

[0212]35A, 35B magnet

[0213]36 end plate

[0214]41 closed casing (case)

[0215]42A, 42B planar spring

[0216]42C center portion

[0217]42D, 42E distal end

[0218]42F, 42G arm portion

[0219]43 linear motor

[0220]44 lubricating oil

[0221]48 compression chamber

[0222]51 cylinder

[0223]51A inner face

[0224]52 piston

[0225]53 compressor body

[0226]54 cylinder head

[0227]54A high-pressure chamber

[0228]55 suction muffler

[0229]55A tube portion

[0230]57 stationary unit

[0231]58 moving unit

[0232]59 resonance spring

[0233]61 ball joint

[0234]64 suspension spring

[0235]66 capillary tube

[0236]71 piston

[0237]72 compliance rod

[0238]81 cylinder

[0239]81A internal face

[0240]81B gas passage

[0241]82 gas bearing

[0242]91 cylinder

[0243]91A surface

[0244]96 piston

[0245]121, 122 mover

[0246]121A core portion

[0247]121B sheet portion

[0248]124 moving iron core

[0249]126A, 126B moving shaft

[0250]128A, 128B flexure bearing

[0251]129A, 129B, 129C, 129D magnet

[0252]130A, 130B coil spring

[0253]131A, 131B spring holders

[0254]131C generally closed space

[0255]132A, 132B spring adapter

[0256]134 cylinder cover

[0257]137 linear motor

[0258]139A, 139D piston

[0259]139B suction passage

[0260]139C suction valve mechanism

[0261]141 D-line

[0262]142, 142A, 142B cylinder

[0263]144 discharge valve mechanism

[0264]145 discharge spring

[0265]146 second suction tube

[0266]146A one end

[0267]146B other end

[0268]147A self-lubricating material

[0269]147B ceramic material

[0270]149 compression mechanism unit

[0271]150 suspension spring

[0272]151 top spring

[0273]152 dynamic absorber

[0274]153 weight

[0275]154, 154A, 154B spring

[0276]155 holder

1. A linear motor comprising: a stator having a stationary iron core anda magnet wire retained on the stationary iron core; a mover positionedon the inner side of the stator and having a moving iron core and amagnet; and a plate-shaped elastic member for supporting the mover in amanner to rock in rocking directions of the mover.
 2. A linear motoraccording to claim 1, wherein the elastic member supports the mover in amanner to confront the stator while keeping a predetermined clearancefrom magnet poles of the stator.
 3. A linear motor according to claim 1,wherein the elastic member is one of a plurality elastic members, theelastic members are arranged on the two sides of the rocking directionsof the mover.
 4. A linear motor according to claim 1, wherein theelastic member is composed of a planar spring.
 5. A linear motoraccording to claim 4, wherein the mover has a cylindrical shape, andwherein the planar spring has a plurality of arm portions extended whileturning in the same direction from the position at which the armportions are mounted on the mover, to the position at which the armportions are mounted on the stator.
 6. A linear motor according to claim5, wherein the planar spring is one of a plurality planar springs,wherein the planar springs are arranged on two sides of the rockingdirections of the mover, and wherein the planar springs are mounted withsuch a deviation in the turning direction that the positions of the armportions are not identical to each other, as viewed in the axialdirection of the mover.
 7. A linear motor according to claim 1, whereinthe elastic member is composed of a flexure bearing having a pluralityof arms.
 8. A linear motor according to claim 1, wherein a magnet poleformed on the inner side of the stator and an outer circumference of themover are so cylindrical as to share the axes with the mover.
 9. Alinear motor according to claim 1, further comprising: a coil springretained at its one end by the mover; and a spring holder fixed on thestator for retaining an other end of the coil spring.
 10. A linear motoraccording to claim 9, further comprising: a moving shaft formed toextend in the rocking directions of the mover.
 11. A linear motoraccording to claim 1, further comprising: at least two coil springs forurging the mover to two sides of the rocking directions of the mover.12. A linear motor according to claim 9, wherein in a stationary state,the coil spring has a compression size of at least one half of therocking distance of the mover.
 13. A linear motor according to claim 9,wherein the spring holder has a closed space for housing the elasticmember and the coil springs therein.
 14. A linear compressor comprising:a linear motor including: stator having a stationary iron core and amagnet wire retained on the stationary iron core; a mover positioned onthe inner side of the stator and having a moving iron core and a magnet;and a plate-shaped elastic member for supporting the mover in a mannerto rock in the rocking directions; a cylinder having an axis shared inthe rocking directions of the mover; and a piston inserted reciprocallyin the cylinder and connected to the mover.
 15. A linear compressoraccording to claim 14, wherein it is driven with a frequency near theresonance frequency, which is determined by asses of the stator and themover and by a spring constant of the elastic member.
 16. A linearcompressor according to claim 14, further comprising: a ball joint forconnecting the piston and the mover.
 17. A linear compressor accordingto claim 14, further comprising: a compliance rod made of an elasticmaterial for connecting the piston and the mover.
 18. A linearcompressor according to claim 14, wherein the mover rocks in horizontaldirections.
 19. A linear compressor according to claim 14, wherein thelinear compressor is free of lubricating oil.
 20. A linear compressoraccording to claim 14, wherein a sliding portion between the piston andthe cylinder is constructed of a gas bearing.
 21. A linear compressoraccording to claim 14, wherein at least one of the piston and thecylinder is made of a self-lubricating material.
 22. A linear compressoraccording to claim 14, wherein at least one of the piston and thecylinder is made of a ceramic material.
 23. A linear compressoraccording to claim 14, further comprising: at least two coil springs forurging the mover toward two sides of the rocking directions of themover.
 24. A linear compressor according to claim 23, wherein thecylinder is inserted and arranged at least partially in the coilsprings.
 25. A linear compressor according to claim 14, wherein themover rocks in directions identical to the gravitational direction. 26.A linear compressor according to claim 14, further comprising: a closedcasing for housing the linear motor, the cylinder and the pistontherein; and a dynamic absorber mounted in the closed casing and havinga spring made elastically deformable in the rocking directions of themover, and a weight attached to the spring.
 27. A linear compressoraccording to claim 26, wherein the dynamic absorber is disposed in atleast one of an upper space and a lower space in the closed casing. 28.A linear compressor according to claim 26, wherein the closed casing hasan inner side formed into a generally cylindrical shape, and wherein theweight is formed into either a generally annular shape or a generallyarcuate shape along the inner side of the closed casing.
 29. A linearmotor according to claim 11, wherein in a stationary state, the coilsprings have a compression size of at least one half of the rockingdistance of the mover.